We’ve had computation using slime mold and soap film, now we have computation using water droplets. Stanford bioengineers have built a “fully functioning computer that runs like clockwork - but instead of electrons, it operates using the movement of tiny magnetised water droplets.”

By changing the layout of the bars on the chip it's possible to make all the universal logic gates. And any Boolean logic circuit can be built by moving the little magnetic droplets around. Currently the chips are about half the size of a postage stamp and the droplets are smaller than poppy seeds.

What all this means I'm not sure, but pavo6503 has a comment that helps understand what's going on:

Logic gates pass high and low states. Since they plan to use drops of water as carriers and the substances in those drops to determine what the high/low state is they could hypothetically make a filter that sorts drops of water containing 1 to many chemicals. Pure water passes through unchanged. water with say, oil in it, passes to another container, water with alcohol to another. A "chip" with this setup could be used to purify water where there are many contaminants you want separated.